If Nintendo were to support a "Create-a-game" application, I'd highly suggest that they use the
Game Maker as a model. Game Maker's very professional, easy to learn, but difficult to master. It's also quite sophisticated for a (mostly) free game development tool, with further expandibillity readily accessible for those who are interested and knowing. There are some people(including myself), who have been able to entirely recreate portions of Mario, Zelda, and even Metroid with all of the quality and polish you'd expect from Nintendo. Not to mention its only around 10 megabytes, with each Game Maker .exe being around 1-7 megabytes.
I think indie development should be heavily supported by Nintendo, but unfortunately I don't see it happening. Microsoft seems to be taking a far greater stance on it, and so Microsoft may win me over as a potential developer in the future. XNA just makes indie game development so much easier. I cannot wait until I can begin building some prototype games for the XBox 360.